Add ContentUnavailableView to Education page (#94)

# Add ContentUnavailableView to Education page

## ♻️ Current situation & Problem
This is just a copy of the changes made in #90 - This is mostly trying
to debug why tests are failing by simply recreating the same changes and
checking if the CI reacts differently here...


## ⚙️ Release Notes 
- Handle Education Video fetching failure with content unavailable view
(#90) by @PaulGoldschmidt


## 📚 Documentation
*Please ensure that you properly document any additions in conformance
to [Spezi Documentation
Guide](https://github.com/StanfordSpezi/.github/blob/main/DOCUMENTATIONGUIDE.md).*
*You can use this section to describe your solution, but we encourage
contributors to document your reasoning and changes using in-line
documentation.*


## ✅ Testing
*Please ensure that the PR meets the testing requirements set by CodeCov
and that new functionality is appropriately tested.*
*This section describes important information about the tests and why
some elements might not be testable.*


### Code of Conduct & Contributing Guidelines 

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of
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ENGAGEHF/Education/Education.swift

@@ -20,7 +20,18 @@ struct Education: View {
         @Bindable var navigationManager = navigationManager
 
         NavigationStack(path: $navigationManager.educationPath) {
-            VideoList(videoCollections: videoManager.videoCollections)
+            Group {
+                let videoCollections = videoManager.videoCollections.filter { !$0.videos.isEmpty }
+                if videoCollections.isEmpty {
+                    ContentUnavailableView(
+                        "No Educational Videos",
+                        systemImage: "video.slash",
+                        description: Text("There are currently no educational videos available.")
+                    )
+                } else {
+                    VideoList(videoCollections: videoCollections)
+                }
+            }
                 .accessibilityIdentifier("Video List")
                 .navigationTitle("Education")
                 .toolbar {

ENGAGEHF/Resources/Localizable.xcstrings

@@ -410,6 +410,9 @@
     },
     "No Data" : {
 
+    },
+    "No Educational Videos" : {
+
     },
     "No medication recommendations" : {
 
@@ -646,6 +649,9 @@
     },
     "The user isn't currently set up correctly. Please try closing the app and opening it back up." : {
 
+    },
+    "There are currently no educational videos available." : {
+
     },
     "Thumbnail Image: %@" : {